1. Technical Field
The present disclosure relates to tensioner apparatus. In particular, the disclosure relates to ribbon supply tensioners for use in printing apparatus.
2. Description of the Related Art
In modern printers, a variety of feed and take-up mechanisms are required to be driven and/or wound in order to transport printing media, ribbon, backings, etc. In most applications, these feed and take-up mechanisms require tensioning structure to maintain a desired amount of tension on the transport system and to minimize or eliminate roll out. One structure used in the art to provide tension is a clutch mechanism. Such a mechanism typically includes a friction plate intended to impart a predetermined torque to the feed and/or take-up mechanisms during operation. See, for example, U.S. Pat. No. 4,797,690. Although adequate for their intended function, these clutch mechanisms are typically expensive and require several assembly/adjustment steps to insure proper operation.
One simple and inexpensive tensioning mechanism is the wrapped coil spring developed by Fargo Electronics Inc. for a ribbon supply system in the Prodigy Plus.TM. thermal transfer printers. In that system, a single coil spring was wrapped around a pulley connected to the ribbon supply system. Each end of the spring was anchored to the housing such that about 180.degree. of the periphery of the pulley was continually engaged by the spring. In this manner, a continuous tensioning was applied and was directly proportional to the spring constant K of the coil spring and the length of extension. While this system was adequate and inexpensive, it did not allow for adjustments for different media and gave little or no recoil when the pulley direction was reversed. Thus, wrinkling and/or tearing or the ribbon supply could result.
Accordingly, a need exists in the art for a simple, versatile, adjustable tensioning system which is configurable for different media and can impart a useful degree of recoil regardless of rotational direction.